DEAR DOCTOR K:

There have been a few cases of croup in my son's day care. I'm sure it's just a matter of time before my son gets it. What do I need to know?

DEAR READER:

Croup is a fairly common illness in children in the age range of 3 months to 3 years. It is unusual in kids older than 6. It results in a hoarse voice and loud, raspy breathing. Taking in a deep breath, which should be nearly silent, instead is quite noisy. The most recognizable symptom is a harsh, brassy cough that sounds like a seal's bark.

Croup is an infectious respiratory illness, usually caused by a virus. The virus first infects the throat, then spreads down the back of the throat to the voice box (larynx) and then to the breathing tube (trachea) that leads to the lungs. The lining of the throat, larynx and trachea become inflamed.

The virus spreads easily from an infected child to an uninfected one through coughing and sneezing. It also can travel on dirty hands, used tissues, toys, drinking glasses and eating utensils. If an uninfected child touches one of these infected objects, and then puts his fingers into his nose or mouth, it can launch the infection.

Children with croup often have a low-grade fever and mild cold symptoms, such as a runny nose and nasal congestion, before the barking cough and raspy breathing begin.

If your son develops croup, your doctor probably will recommend the following to ease his breathing until the infection goes away:

-- Rest or quiet play;

-- Ibuprofen (Advil, Motrin) or acetaminophen (Tylenol) to relieve any discomfort;

-- Drinking plenty of fluids. This will prevent mucus in his lungs from getting thick and difficult to cough up.

-- A cool mist vaporizer. Cool mist soothes and moistens the inflamed airways and helps mucus drain.

Symptoms of croup usually go away within three to five days. A mild cough may last a bit longer. In some cases, your doctor also may prescribe corticosteroid drugs. These will help reduce inflammation of the airway.v It's very infrequent, but croup sometimes can cause severe breathing problems. If your son does catch croup, there are several red-flag signs to watch for. Is he having trouble breathing? When he takes in a deep breath, is it noisy? Are his lips or fingernails a blue hue? Has he developed a suddenly increased fever (a possible sign that bacteria have infected lungs weakened by the virus)? Does he seem unusually pale? Is he listless?

If you see any of these danger signs, call for emergency help immediately, or take your son to an emergency room.

Fortunately, croup almost always clears up after several days and leaves no lasting damage. On the unusual occasions when it becomes serious, rapid medical care nearly always turns around a potentially dangerous situation.

(Dr. Komaroff is a physician and professor at Harvard Medical School. Go to his website to send questions and get additional information: www.AskDoctorK.com.)

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